Method and system for controlling a mechanical pump to monitor and optimize both reservoir and equipment performance

Abstract

Method and apparatus for optimizing the overall production efficiency of any pumping well based on accurate measurements of the time-averaged rate that fluid exists the wellhead. The improved apparatus includes temperature compensated, hermetically sealed electronic sensors that accurately measure the instantaneous rate of both pulsating and steady-state flow, and devices for processing measured flow-rate information to ascertain the performance of downhole equipment and fluid reservoirs. The apparatus is self-calibrating on any well, and automatically compensates for normal changes in both downhole equipment and reservoir performances that typically limit the operation of conventional well-control devices. The apparatus may be easily installed at ground level without major changes to existing wellhead equipment, and readily adapts to the efficient control of pumping equipment utilized with any other type of fluid reservoir.

What is claimed is: 
     
       1. In a system for preventing damage resultant from pump-off of a well pump for pumping an essentially incompressible fluid mixture made up of a substantially homogeneous mingling of solids, liquids and gases, said liquids constituting the major portion of said mixture, the relative proportions of said solids, liquids and gases being subject to change over time, from a well casing replenished by the fluid mixture from a surrounding earth formation, a flow-rate sensor for measuring in real time the volumetric flow-rate of the fluid mixture, said sensor comprising: housing means having an internal fluid passageway, and inlet and outlet ports, said passageway for directing said fluid mixture between said inlet and outlet ports;   a backpressure valve means in fluid communication with said passageway for maintaining a wellhead discharge pressure at or above the highest bottom hole pressure that will act upon the downhole inlet of the well pump at any time during a regular pump operating cycle as said mixture passes through said passageway;   a barrier wall defined within said passageway, said wall including a fixed area orifice through which all of said mixture passes from said inlet port to said outlet port;   a smooth seating surface surrounding the outlet side of said orifice;   a flow-sensing element mounted for movement within said passageway and operative between first and second positions, said element oriented to assure that the movement of said element from said first position is proportional to the velocity of said mixture as said mixture passes through said passageway from said inlet port to said outlet port, said element including a substantially planar surface that completely covers said fixed area orifice when said element is in said first position, said planar surface having a sealing surface that mates with said seating surface for providing a tight seal when said element is in said first position; and   transducer means for producing an electrical signal that is continuously proportional to the real time movement of said sensing element.   
     
     
       2. The flow-rate sensor of claim 1, further comprising signal-compensating means for adjusting the magnitude of said electrical signal to take into account variations in at least one of the pressure, temperature, density and viscosity of said fluid mixture. 
     
     
       3. The flow-rate sensor of claim 1, wherein said flow-sensing element is in said first position when the velocity of mixture is at zero. 
     
     
       4. The flow-rate sensor of claim 1, further comprising means for calibrating said electrical signal to a known standard of reference. 
     
     
       5. The flow-rate sensor of claim 4, wherein said standard of reference is the known average mass-density and viscosity of said fluid mixture. 
     
     
       6. The flow-rate sensor of claim 1, wherein said angle of deflection is linearly related to said velocity of said mixture. 
     
     
       7. The flow-rate sensor of claim 1, wherein said transducer means comprises: magnetic field generating means connected to said flow-sensing element for pivotal movement therewith; and   magnetic field sensing means positioned adjacent said magnetic field generating means for producing said electric signal that is continuously proportional to the angular deflection of said sensing element.   
     
     
       8. The flow-rate sensor of claim 7, wherein said magnetic field sensor means comprises a Hall-effect sensor. 
     
     
       9. The flow-rate sensor of claim 7, wherein said housing further comprises a chamber for isolating said magnetic field sensing means from said fluid mixture. 
     
     
       10. The flow-rate sensor of claim 9, wherein said magnetic field sensing means is in close proximity to said magnetic field generating means and a portion of said chamber is made up of a non-magnetic barrier disposed between said sensing means and said means for accomplishing the isolation of said sensing means from said fluid mixture. 
     
     
       11. The flow-rate sensor of claim 1, further comprising compensating means for adjusting said electrical signal to produce a calibrated output signal that is linearly related to the volumetric flow-rate of the fluid mixture as it passes through said passageway. 
     
     
       12. The flow-rate sensor of claim 11, further comprising means for rendering said compensating means insensitive to ambient temperature outside of said housing and to the temperature of the fluid mixture. 
     
     
       13. The flow-rate sensor of claim 1, wherein said backpressure valve means is located downstream of said passageway. 
     
     
       14. The flow-rate sensor comprising: a check valve having a housing containing an internal chamber, with inlet and outlet openings for directing fluid through said chamber, and a flapper pivotally mounted within said chamber and exposed to fluid flowing therethrough, an angle of deflection of the flapper being a function of the instantaneous rate of fluid through said chamber;   an enclosure extending from said valve housing and containing a cylindrical magnet and Hall-effect sensor;   a pivot pin passing through said housing and said enclosure and connected to said flapper and said magnet;   one end of said magnet having an axial bore formed therein, the Hall-effect sensor positioned within said bore, the magnetic poles of said magnet formed on opposite sides of said end of said magnet; and   said Hall-effect sensor being located within a jacket formed of a non-magnetic material, the jacket in turn positioned within said enclosure, a fluid impervious seal being retained between said jacket and said enclosure.   
     
     
       15. The flow-rate sensor of claim 14, further comprising temperature sensing means positioned within said jacket in close proximity to said Hall-effect sensor so that said temperature sensing means and said Hall-effect sensor are exposed to the same temperature at all times. 
     
     
       16. The flow-rate sensor of claim 14, wherein said temperature sensing means comprises a zener diode. 
     
     
       17. The flow-rate sensor of claim 14, further comprising compensating means for adjusting said electrical signal to produce a calibrated output signal that is linearly related to the volumetric flow-rate of the fluid mixture as it passes through said passageway. 
     
     
       18. The flow-rate sensor of claim 17, further comprising means for rendering said compensating means insensitive to ambient temperature outside of said housing and to the temperature of the fluid mixture.